1. Field of the Invention
The present invention generally relates to a CT (computerized tomographic) scanning apparatus selectively driven by a DC power source and an AC power source. More specifically, the present invention is directed to a CT scanner temporarily driven by secondary (rechargeable) batteries during scanning operation.
2. Description of the Related Art
As is known in the CT scanner field, power supply facilities installed in CT scanners such as an X-ray CT (computerized tomographic) imaging apparatus, normally and directly supply high power that is received from a commercial power supply, e.g., a three-phase power supply, to a high-power consumption low unit thereof. This high-power consumption load unit includes an X-ray tube driving unit, a gantry driving unit, and a couch driving unit. These driving units excluding the couch driving unit require high or peak power while scanning a biological body under medial examination laid on the couch.
Under such circumstances, the power supply facilities of the conventional CT scanners must be designed to have high power capacities in order that peak power (e.g., 30 kW) required during the scanning operation is available, which is extremely higher than the power required the non-scanning operation, for instance, ten to several tens times higher than the normal power (e.g., 3 kW). In other words, the power supply facilities of the conventional CT scanners can sufficiently supply such peak power to the high power consumption unit during at least the scanning operation.
As a result, since the conventional power supply facilities must be designed to allow peak power, or high power capacities, such conventional power supply facilities become very expensive. For instance, the rated power of the power cables must be designed to withstand such peak power. Moreover, to maintain such high-power consumption facilities, higher expense must be paid to power supply firms.
There are further problems in the conventional high power facilities in view of total efficiencies of the power supply facilities. For instance, assuming now that the typical operation time period of one conventional CT scanner is about 8 hours in one day and 200 scanning operations are to be performed within eight operation-hours, since one scanning operation practically requires approximately 3 seconds, the entire scanning operation in one day requires only approximately 600 seconds (i.e., 10 minutes). That is, such high peak power is required only for 10 minutes, namely 1/48 (=10/8.times.60) of the entire operation time per day. Nevertheless, the conventional power supply facilities must have high power capacities capable of supplying such peak power.